As radiation detection panels, X-ray detection panels have recently been put to practical use. The X-ray detection panels include a fluorescent film for converting an X-ray (radioactive ray) into light, and a photoelectric conversion element for converting the light into an electric signal. Such X-ray detection panels can contribute to reduction of the size of the entire X-ray flat detector, compared to conventional X-ray image tubes. The X-ray flat detector converts, into digital electric information, the image information corresponding to the X-rays having passed through an inspection target. The X-ray flat detector can provide various digital information processing functions, such as digital image processing and digital image storage.
The X-ray flat detector is widely used for various purposes, such as medical and dental treatments of patients, industrial inspections including nondestructive inspections, scientific researches including architectural analysis. In these fields, high-precision image extraction and high-speed image detection are possible by digital information processing, with the result that the amount of undesirable X-ray (radioactive ray) exposure can be reduced, and prompt inspection, prompt diagnosis, etc., can be realized.
Scintillator material techniques are often diverted to the forming of a fluorescent film for the X-ray flat detector. In the X-ray flat detector, a scintillator material is formed of a material containing, as main components, cesium (Cs) and iodine (I) used in the conventional X-ray image tubes. The scintillator material, which contains cesium iodide (CsI) as a main component and is to be grown into columnar crystals, can enhance sensitivity and resolution by virtue of optical guide effect, compared to another scintillator material forming granular crystals.
To secure the X-ray flat detector in a highly sensitive state, it is necessary to acquire light (fluorescent light) of a sufficient intensity, into which an X ray is converted, and to form the fluorescent film to a certain thickness. When a scintillator material containing CsI as a main component is used, the fluorescent film may often be formed to a thickness of about 500 μm.
On the other hand, the fluorescent film has a tendency to reduce the resolution of an image when its thickness is increased. In order for the fluorescent film to simultaneously have high sensitivity and high resolution, it is desirable to employ a deposition method capable of forming thinner columnar crystals of the scintillator material and forming the columnar crystals more uniformly in the thickness direction.
The conventional X-ray image tube manufacturing method and the conventional X-ray flat detector manufacturing method disclose film forming methods associated with scintillator materials. Further, as a similar manufacturing method, a method of manufacturing a radiation image conversion panel using photostimulable phosphor is well known.
A manufacturing apparatus for depositing evaporated scintillator material particles on the surface of a photoelectric conversion substrate comprises a vacuum chamber and a crucible placed in the vacuum chamber. When depositing the scintillator material, the photoelectric conversion substrate is arranged horizontally above the crucible in the vacuum chamber. After that, the scintillator material is heated in the crucible and evaporated therefrom. As a result, the evaporated scintillator material is deposited on the surface of the photoelectric conversion substrate. There is a case where the evaporated scintillator material is deposited on the surface of the photoelectric conversion substrate, with the photoelectric conversion substrate kept rotated on a horizontal plane.